Equinus is typically described as a condition in which the upward bending motion of the ankle is limited. Equinus is defined as the inability or lack of ankle joint dorsiflexion less than a right angle relative to the leg.
Equinus may result in a lack of flexibility past the right angle relative to the leg. Someone suffering with equinus may lack the flexibility to bring the top of foot 18 past a right angle (90°) relative to the leg and toward the front of the leg. A typical maximum ankle range of motion for dorsiflexion is indicated as twenty-five degrees (25°) less than a right angle relative to the leg. Equinus may also be characterized as a limited ankle range of motion for dorsiflexion which is no more than five (5°), ten (10°) or even fifteen degrees (15°) less than a right angle relative to the leg.
There are several possible causes for limited range of ankle motion. Limited range of ankle motion is often due to tightness in the calf muscles (the soleus muscle and/or the gastrocnemius muscle). Shortening of the gastrocnemius muscle (also known as gastroc equinus) is a very common condition which may affect most people because the gastrocnemius muscle crosses two joints. The gastrocnemius muscle originates above knee 12 joint, while the soleus originates below knee 12 joint. Both muscles join to form the Achilles tendon, which attaches to the heel. Therefore, the gastrocnemius muscle crosses two joints: knee 12 and the ankle, while the soleus muscle only crosses the ankle joint.
Regardless of the cause of limited ankle motion, someone suffering with equinus can develop a wide range of foot problems. There are several ways to treat limited ankle range of motion, such as gastroc equinus, including stretching exercises, orthotics with heel lifts, padding, molded shoes, serial casting, as well as night splints and braces.
Many current night splints allow user 22 to sleep with their knees bent. Current night splints and braces do not lock knee 12 into extension as they do not extend above the knee. Failure to lock knee 12 into extension means that a person experiencing gastroc equinus does not stretch gastrocnemius muscle, and therefore is only stretching the soleus muscle.
Many current night splints and braces are awkward and uncomfortable for sleeping. Since night splints and many current braces are supposed to be worn throughout the night, an awkward or cumbersome night splint or brace may cause a user to either not get a good night's sleep or cause a user to remove the device. If user 22 does not get a good night's sleep, user 22 may not choose to use the device in the future. This lack of compliance leads to the current devices not performing their intended function.
Even if a knee is kept completely straight by a user, the night splint or brace is not the reason for a complete stretch of gastrocnemius muscle, because there is no above the knee extension locking the knee joint.
If the night splint or brace does not lock the knee in full extension while dorsiflexing the ankle joint, the device is not providing the preferred method of treatment.